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United States Patent |
6,087,076
|
Sakai
,   et al.
|
July 11, 2000
|
Method of manufacturing semiconductor devices by performing coating,
heating, exposing and developing in a low-oxygen or oxygen free
controlled environment
Abstract
A method of manufacturing semiconductor devices includes a coating step for
coating a substrate using a resist solution including a base resin and a
low-oxygen or oxygen-free solvent in which oxygen is removed by nitrogen
bubbling, a heating step for heating the substrate coated with the resist,
an exposing step for exposing the substrate with radiation to transfer a
pattern, and a developing step for developing the exposed substrate. The
coating step, the heating step, the exposing step and the developing step
are performed under an environment controlled in a low-oxygen or
oxygen-free state.
Inventors:
|
Sakai; Keita (Utsunomiya, JP);
Chiba; Keiko (Utsunomiya, JP);
Maehara; Hiroshi (Yokohama, JP)
|
Assignee:
|
Canon Kabushiki Kaisha (Tokyo, JP)
|
Appl. No.:
|
968589 |
Filed:
|
November 13, 1997 |
Foreign Application Priority Data
Current U.S. Class: |
430/327; 430/330; 438/758 |
Intern'l Class: |
G03C 005/00 |
Field of Search: |
430/327,330
438/758
|
References Cited
U.S. Patent Documents
5723259 | Mar., 1998 | Oikawa et al. | 430/330.
|
Primary Examiner: Nuzzolillo; Maria
Assistant Examiner: Weiner; Laura
Attorney, Agent or Firm: Fitzpatrick, Cella, Harper & Scinto
Parent Case Text
This application is a divisional of copending application Ser. No.
08/621,648, filed Mar. 26, 1996.
Claims
What is claimed is:
1. A method of manufacturing semiconductor devices, comprising:
a coating step for coating a substrate using a resist solution including a
base resin and a low-oxygen or oxygen-free solvent in which oxygen is
removed by nitrogen bubbling;
a heating step for heating the substrate coated with the resist;
an exposing step for exposing the substrate with radiation to transfer a
pattern; and
a developing step for developing the exposed substrate,
wherein said coating step, said heating step, said exposing step and said
developing step are performed under an environment controlled in a
low-oxygen or oxygen-free state.
2. A method according to claim 1, wherein the environment is an atmosphere
of an inert gas.
3. A method according to claim 2, wherein the inert gas is selected from
the group consisting of neon, argon, krypton, xenon, radon, nitrogen, and
helium.
4. A method according to claim 1, further comprising baking the resist in
the environment, after said exposing step.
5. A method according to claim 1, wherein said exposing step comprises
using an excimer laser light source as an exposure light source.
6. A method according to claim 1, wherein the resist is a chemical
amplification resist.
7. A device produced by a process comprising the method as set forth in any
one of claims 1 to 6.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a photoresist used in photolithography,
and treatment techniques of the resist.
2. Related Background Art
There is no end to the pursuit of higher integration density of micro
devices such as semiconductor devices, and processing applying the
photolithography technology is demanded to achieve further finer
patterning. Light sources used in exposure apparatus are thus switching
from the conventional i-line light sources such as a mercury lamp to KrF
and ArF excimer laser light sources of shorter wavelengths. Further,
chemical amplification type resists with higher resolution are drawing
attention as resists used in that case.
However, because the excimer laser light has very high irradiation energy,
there is a possibility of taking place a reaction of a base resin itself,
which did not take place with the conventional i-line. For example, in the
case of the KrF excimer laser, novolak or polyvinyl phenol, used as a base
resin of a resist, is oxidized by exposure to the KrF excimer laser. In
more detail, activation energy of oxidation of the phenol is about
2.8.times.10.sup.-20 (J), while energy (hv) of the KrF excimer laser is
8.01.times.10.sup.-19 (J). This thus explains why the energy of the
excimer laser causes the oxidation.
Quinones produced by this oxidation have absorption at wavelengths near 300
nm, and thus decrease the transmittance in the wavelength region of the
KrF excimer laser. The decrease of transmittance will raise the problem
that an adequate profile cannot be achieved when the resist is developed.
Further, the oxidation of the base resin will result in changing the
dissolving rate thereof into a developer, which, in turn, will raise
problems of changing the sensitivity and changing the resist line width
transferred.
SUMMARY OF THE INVENTION
The present invention has been accomplished to solve the above problems,
and an object of the invention is to enable high-accuracy pattern transfer
while preventing a decrease of transmittance of a resist and suppressing
the oxidation of a resist.
An aspect of the present invention, solving the above problems, is a resist
composition characterized by using a low-oxygen or a oxygen-free solvent.
A low-oxygen state mentioned herein means that an oxygen volume in 1 ml of
a solution is preferably 0.05 cm.sup.3 or less under an atmospheric
pressure, and more preferably 0.03 cm.sup.3 or less.
A solvent used in the resist may be one of the of types solvents used in
the conventional resists. These solvents are, for example, ethylene glycol
based solvents such as ethylene glycol monomethyl ether, ethylene glycol
monoethyl ether, and diethylene glycol dimethyl ether, and acetic esters
thereof, including ethylene glycol monomethyl ether acetate and ethylene
glycol monoethyl ether acetate; propylene glycol based solvents such as
propylene glycol monomethyl ether and propylene glycol monoethyl ether,
and acetic esters thereof, including propylene glycol monomethyl ether
acetate and propylene glycol monoethyl ether acetate; aliphatic ketones
such as acetone, methyl ethyl ketone, methyl isobutyl ketone, pentanone,
and isoamyl acetate, alicyclic ketones such as cyclohexane, aromatic
compounds such as toluene and xylene, etc., which can be used singly or as
a mixture. It is noted that any other solvent than these solvents can be
used without any specific limitations as long as it can dissolve solid
components of the resist.
Another aspect of the present invention is characterized in that an
antioxidant is contained in the resist composition.
The antioxidant may be one selected from monophenol based compounds such as
2,6-di-t-butyl-p-cresol, bisphenol based compounds such as 2,2'methylene
bis(4-methyl-6-t-butylphenol), and polymer type phenol based compounds
such as 1,1,3-tris(2-methyl-4-hydroxy-5-t-butylphenyl)butane. Furthermore,
the antioxidant may be one selected from sulfur based antioxidants such as
dilauryl 3,3'thiodipropionate, and phosphorus based antioxidants such as
triphenylphosphite. In addition, the antioxidant may be one selected from
compounds including erythorbic acid, isopropyl citrate, and
nordihydroguaiaretic acid.
Still another aspect of the present invention is characterized in that an
environment for performing at least one of an application treatment of the
resist, a heat treatment, an exposure treatment, and a development
treatment is controlled in a low-oxygen or oxygen-free state using, for
example, an inert gas.
An example of a method for controlling the environment in the low-oxygen or
oxygen-free state is to replace the air in the apparatus with the inert
gas. Preferred examples of the inert gas applicable herein are neon,
argon, krypton, xenon, radon, nitrogen, helium, and so on.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a schematic drawing to show a production line of a device;
FIG. 2 is a schematic drawing of a resist applying apparatus;
FIG. 3 is a schematic drawing of a heat-treating apparatus;
FIG. 4 is a schematic drawing of an exposure apparatus;
FIG. 5 is a drawing to show a flow for fabricating semiconductor devices;
and
FIG. 6 is a drawing to show a flow of a wafer process.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
<Embodiments of Treatment Apparatus>
The embodiments of the present invention will be explained. FIG. 1 is a
schematic drawing of a production line for producing micro-devices such as
semiconductor products, in which there are a resist applying/developing
apparatus 100, a resist heat-treating apparatus 101, and an exposure
apparatus 102 arranged in order and in which in-line interfaces 103, 104
for transfer of a substrate are provided between respective ones of the
apparatus. A substrate is carried along a direction shown by the arrows in
the drawing to be processed in order by the apparatus.
FIG. 2 is a schematic drawing of the resist applying/developing apparatus
(coater developer), in which numeral 1 denotes a chamber, 2 the resist, 3
the wafer substrate, and 4 a spinner for rotating the wafer substrate
mounted thereon. A device 5 for dropping a resist solution or a resist
developer is set above the spinner 4. In this arrangement, when the resist
solution or the developer drops onto the wafer substrate 3 rotated by the
spinner 4, the centrifugal force evenly spreads the liquid on the surface
of the substrate. The chamber 1 is provided with an inlet 6 and an outlet
7 for the inert gas (for example, neon, argon, krypton, xenon, radon,
nitrogen, or helium).
Although the drawing shows the separate resist applying/developing
apparatus 100 and heat-treating apparatus 101, they may be incorporated
into a single apparatus.
FIG. 3 is a schematic drawing of the resist heat-treating apparatus, in
which reference numeral 11 designates a chamber, 12 the resist, 13 the
wafer, and 14 a hot plate. The chamber 11 is provided with an inlet 15 and
an outlet 16 for the inert gas (for example, neon, argon, krypton, xenon,
radon, nitrogen, or helium).
FIG. 4 is a schematic drawing of the resist exposure apparatus, in which
reference numeral 21 is a lens barrel, 22 KrF or ArF excimer laser light,
23 a lens, 24 the resist, 25 the wafer, and 26 a chamber. The chamber 26
is provided with an inlet 27 and an outlet 28 for the inert gas (for
example, neon, argon, krypton, xenon, radon, nitrogen, or helium).
The following describes examples of the resist treatments in the respective
apparatus in the above production line.
EXAMPLE 1
The resist was a chemical amplification type resist. The base resin was
novolak, a crosslinking agent was hexamethylolmelamine, and a photoacid
generator was an onium salt. These were also used in Example 2 and
subsequent examples as described below.
First, the solvent, ethylene glycol monoethyl ether acetate, was subjected
to nitrogen bubbling to lower the concentration of oxygen, thereby
obtaining a resist solution of the low-oxygen or oxygen-free resist
composition.
After that, using the resist applying/developing apparatus of FIG. 2, the
resist solution was dropped as while rotating the wafer by the spinner 4,
thereby evenly applying the resist on the wafer. Pre-bake was next carried
out on the hot plate 14, using the heat-treating apparatus of FIG. 3.
Then, using the exposure apparatus of FIG. 4, the wafer was subjected to
exposure to the KrF excimer laser light to effect transfer of a pattern of
a reticle (not shown). After the exposure transfer, post-exposure bake was
carried out on the hot plate in the apparatus of FIG. 3. After that, using
the resist applying/developing apparatus of FIG. 2, the developer was
dropped onto the resist while rotating the wafer by the spinner 4, thereby
performing the development treatment.
Using the ultraviolet and visible spectrophotometer, the spectral
transmittance of the resist film was measured in the wavelength region of
400 nm or less, and it was confirmed that the transmittance of the resist
using the low-oxygen solvent of this example showed no change before and
after the exposure.
Next, using a Fourier transform infrared spectrophotometer (FTIR), infrared
absorption was measured of the quinones resulting from the oxidation of
the base resin. The wave numbers were near 1700 cm.sup.-1 and 1200
cm.sup.-1. The results assured that the resist using the low-oxygen or
oxygen-free solvent of this example was more restrained in oxidation than
the resists using the conventional solvents.
Namely, it was confirmed that the present example using the chemical
amplification type resist with the low-oxygen solvent realized
high-accuracy pattern transfer without lowering the transmittance of the
resist, while suppressing the oxidation of the resist.
EXAMPLE 2
2,6-di-t-butyl-p-cresol was added as an antioxidant into the resist
solution and the resultant solution was applied onto the wafer, using the
apparatus of FIG. 2. Subsequently, conducted were the pre-bake in the
apparatus of FIG. 3, the exposure transfer in the exposure apparatus of
FIG. 4, the post-exposure bake in the apparatus of FIG. 3, and the
development treatment in the apparatus of FIG. 2.
The spectral transmittance of the resist film was measured in the
wavelength region of 400 nm or less, using the ultraviolet and visible
spectrophotometer, which assured that the transmittance of the resist with
the antioxidant mixed therein showed no change before and after the
exposure.
Next, using the Fourier transform infrared spectrophotometer (FTIR),
infrared absorption was measured of the quinones resulting from the
oxidation of the base resin. The results showed that the resist with the
antioxidant mixed therein was more restrained in oxidation than the resist
without mixture of the antioxidant.
Namely, it was confirmed that the present example using the resist in which
the resist composition contained the antioxidant realized high-accuracy
pattern transfer without lowering the transmittance of the resist, while
suppressing the oxidation of the resist
EXAMPLE 3
The chamber 1 of the resist applying/developing apparatus of FIG. 2 was
filled with an inert gas (N.sub.2) to produce an environment controlled in
the low-oxygen or oxygen-free state. The resist was applied onto the wafer
under this atmosphere. After that, conducted were the pre-bake, the
exposure transfer, and the post-exposure bake. Then, a wafer was
introduced into the resist applying/developing apparatus to be developed
under the atmosphere of the above inert gas.
The spectral transmittance of the resist film was measured in the
wavelength region of 400 nm or less with the ultraviolet and visible
spectrophotometer, which assured that the transmittance of the resist
applied in the inert gas atmosphere showed no change before and after
exposure.
Next, using the Fourier transform infrared spectrophotometer (FTIR),
infrared absorption was measured of the quinones resulting from the
oxidation of the base resin. The results showed that the resist applied in
the inert gas atmosphere was more restrained in oxidation than the resist
coated in the air.
Namely, it was confirmed that the present example arranged to perform the
application treatment and development treatment of the resist under the
environment filled with the inert gas and thus controlled in the
low-oxygen or oxygen-free state realized high-accuracy pattern transfer
without lowering the transmittance of the resist, while suppressing the
oxidation of the resist.
EXAMPLE 4
The chamber 11 of the resist heat-treating apparatus of FIG. 3 was filled
with an inert gas (N.sub.2) to produce an environment controlled in the
low-oxygen or oxygen-free state. The wafer coated with the resist was
introduced into the resist heat-treating apparatus of FIG. 3 and was
pre-baked in the inert gas atmosphere. Subsequently, exposure transfer was
carried out and post-exposure bake was conducted again in the inert gas
atmosphere. After that, development was carried out.
The spectral transmittance of the resist film was measured in the
wavelength region of 400 nm or less with the ultraviolet and visible
spectrophotometer, which assured that the transmittance of the resist
heat-treated in the inert gas atmosphere showed no change before and after
exposure.
Next, using the Fourier transform infrared spectrophotometer (FTIR),
infrared absorption was measured of the quinones resulting from the
oxidation of the base resin. The results showed that the resist
heat-treated in the inert gas atmosphere was more restrained in oxidation
than the resist heat-treated in the air.
Namely, it was confirmed that the present example for performing the heat
treatment of the resist under the environment filled with the inert gas
and thus controlled in the low-oxygen or oxygen-free state realized
high-accuracy pattern transfer without lowering the transmittance of the
resist, while suppressing the oxidation of the resist.
EXAMPLE 5
The chamber 21 of the exposure apparatus of FIG. 4 was filled with an inert
gas (N.sub.2) to produce an environment controlled in the low-oxygen or
oxygen-free state. The wafer after coated with the resist and pre-baked
was introduced into the chamber of the KrF excimer exposure apparatus
under the inert gas atmosphere and exposure transfer was conducted under
the atmosphere. After that, post-exposure bake and development treatment
were carried out.
The spectral transmittance of the resist film was measured in the
wavelength region of 400 nm or less with the ultraviolet and visible
spectrophotometer, which assured that the transmittance of the resist
exposed in the inert gas atmosphere showed no change before and after
exposure.
Next, using the Fourier transform infrared spectrophotometer (FTIR),
infrared absorption was measured of the quinones resulting from the
oxidation of the base resin. The results showed that the resist exposed in
the inert gas atmosphere was more restrained in oxidation than the resist
exposed in the air.
Namely, it was confirmed that the present example for performing exposure
of the resist in the environment filled with the inert gas and thus
controlled in the low-oxygen or oxygen-free state realized high-accuracy
pattern transfer without lowering the transmittance of the resist, while
suppressing the oxidation of the resist.
EXAMPLE 6
The present example satisfied the conditions including all the features of
the above examples, in which the resist was the chemical amplification
type resist obtained by adding the antioxidant in the low-oxygen or
oxygen-free solvent and in which all the resist applying treatment, resist
heat treatment, exposure treatment, and development treatment were carried
out under the inert gas atmosphere. The same measurements as in the above
examples were carried out using the ultraviolet spectrophotometer and
infrared spectrophotometer, and the results showed that the present
example was able to decrease most of the change of transmittance of the
resist and the oxidation of the resist.
Namely, it was confirmed that the present example satisfying all the
conditions of the above examples realized extremely high accuracy pattern
transfer without lowering the transmittance of the resist, while most
suppressing the oxidation of the resist.
EXAMPLE 7
Next explained is an example of a process for fabricating semiconductor
devices. FIG. 5 is a flowchart to show a fabrication flow of semiconductor
devices (e.g., semiconductor chips such as IC's or LSI's, liquid crystal
panels or CCD's, thin-film magnetic heads, microsyringes, etc.).
At step 1 (design of circuit) the design of a circuit of a semiconductor
device is carried out. At step 2 (production of mask) a mask structure is
fabricated with the designed circuit pattern formed therein. On the other
hand, a wafer is fabricated using a material such as silicon at step 3
(production of wafer). Step 4 (wafer process) is called a pre-process, in
which actual circuits are formed on the wafer by the photolithography
technology using the mask structure and wafer thus prepared. Next, step 5
(assembling) is called a post-process, which is a step for obtaining
semiconductor chips from the wafer fabricated at step 4, and which
includes an assembling step (dicing and bonding) and a packaging step.
Step 6 (inspection) is a step for inspecting the semiconductor devices
produced at step 5 by operation checking tests, durability tests, etc.,
thereof. The semiconductor devices are completed through the above steps
and are shipped (step 7).
FIG. 6 shows the detailed flow of the above wafer process. At step 11
(oxidation) the surface of the wafer is oxidized. At step 12 (CVD) an
insulating film is formed on the surface of the wafer. At step 13
(formation of electrodes) the electrodes are formed by vapor deposition on
the wafer. At step 14 (ion implantation) ions are implanted into the
wafer. At step 15 (resist treatment) the wafer is coated with the resist.
At step 16 (exposure) the circuit pattern of the mask is printed in the
wafer by the excimer exposure method as explained previously. At step 17
(development) the wafer after exposure is developed. At step 18 (etching)
etching is carried out to remove portions other than the resist image
developed. At step 19 (resist stripping) the resist after etching is
removed. By repeating these steps, multiple circuit patterns are formed on
the wafer.
Use of the production process according to the present invention permits
semiconductor devices of high integration density, which were previously
difficult to obtain by the conventional fabrication process, to be
produced.
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